[asterisk-users] Still on spandsp/app_fax and T.38

[Kevin P. Fleming]

Steve Underwood wrote:

> FFA sends its repeating no-signal and preamble packets with incrementing 
> sequence numbers. While its not the only system which does that, it 
> confuses some T.38 implementations. The T.38 spec is too vague to say 
> whether the practice is right or wrong. In other applications of the FAX 
> machine in spandsp, the software has been set up to send multiple copies 
> on the key packets, with the same sequence number for all the copies. 
> This seems to be the most compatible way to send these repeats. I don't 
> know if the UDPTL infrastructure in Asterisk can do that.

No, it can't without some modifications. The Asterisk UDPTL stack
receives raw IFPs from the application, and generates sequence numbers
itself. At this time internal Asterisk frames have no way of being
marked as a 'repeat' frame, or marked as 'send this frame _x_ times',
but that certainly could be done if it was deemed useful and worthwhile.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kpfleming at digium.com
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